Method of cleaning sand filters and appurtenances



Feb. 2, 19 37. .1. e. PATRICK.

METHOD OF CLEANING SAND FILTERS AND APPURTENANCES Filed Dec. 7, 1935 INVENTOR W4 MN 6. PAT/F/CK ATTORK Patented Feb. 2, 1937 UNITED STATES PATENT OFFICE IVIETHOD OF CLEANING SAND FILTERS AND APPURTENANCES Julian G. Patrick, Western Port, Md., assignor to West. Virginia Pulp and Paper Company, New York, N.Y., a corporation of Delaware Application December I, 1935, Serial No. 53,330

4 Claims.

- bodies are either not soluble in the usual water used for back washing nor are they easily dislodged by it. Also when the action of the wash water is relied upon to effect cleaning, it is often necessary to use water under considerable pressure to open up closed orifices of the drain pipes and when the closed jets are unstopped by the action of the water the sudden release of pressure causes displacement of sand and gravel and loss of sand.

I have now discovered that an effective cleaning action is had by the use of sulphur dioxide which, in dilute aqueous solution, 1. e. as'sulfurous acid, HzSOa removes adhering deposits andincrustations without attacking the pipes or other iron work.

In carrying out my invention, I preferably add the sulphur dioxide from any suitable source desirably from a container in which the sulphur dioxide is stored in liquid form, mixing it in regulated quantities with a stream of water flowing in the reverse direction through the filter.

The invention will be best understood by reference to the following detailed description taken with the accompanying drawing, the single fig-- ure of which shows in cross section a water filter of conventional type in the process of being cleaned in accordance with my invention.

In the drawing I denotes the filter receptacle containing a layer of gravel 2 and of sand 3 below which is disposed a distributer system 4 for conveying away the filtered water, the water which is drained from such system being collected in down-take pipes 6 which in turn communicate with pipe I. Also communicating with pipe I is pipe 8 admitting wash water to the filter pipes I and 8 being provided respectively with 'valves 1 and 8'. In the type of filt'er shown, the wash water may be collected in the trough to, which has a suitable inclination to enable the, water collecting therein to drain away.

The supply of SOals preferably admitted to the system so as tobe circulated with the back wash water and for this purpose may be admitted to the pipe I through pipe ll (desirably of brass) leading from the tank l2, the fiow of gas being regulated by means of valve l 3.

In the operation of my improved method after the filters to be cleaned have been taken out of service and the tank I! connected, the S0: is allowed to flow slowly into pipe 1. Previously a water level is established intermediate of the height of the filter as shown by the line a-a preferably by first draining the filter and then adding fresh water throughthe pipe 8 and valve 8. The gas is allowed to fiow until a suitable concentration is had in the filter.

After the solution has been formed in the partly filled filter, the valve i3 is closed and the water level is raised to above the top of the sand by admitting wash water through pipe 8. After a suitable period depending upon particular circumstances including the concentration of SO: in the solution, as for example four and one half to five hours more or less, the reaction is complete whereupon the solution may be removed by admitting wash water through pipe 8 thereby causing the spent solution to be washed into the wash water trough ill; desirably the wash is repeated two or three times or as often as necessary. If necessary, the S02 treatment and washing operations may be repeated. In carrying out the process, the formation of the S0: solution may be hastened somewhat by causing the liquid sulphur dioxide to fiow into the water in the filter as by turning the cylinder l2 upside down.

The concentration of SO: in the water filling the filter may be varied considerably. In practice I have found a concentration as high as 3% to give rapid cleaning action without causing appreciable corrosion of the metal piping. Ordinarily, however, I prefer to use a much weaker concentration as for example as low as .02%.

by the so-called iron bacteria etc. which substances I have found to constitute the bulk of the coating on the sand grains, gravel and the interior of the under drain pipes. The hydrated manganese dioxide is thereby reduced to bivalent manganese which combines withthe oxidized sulfurous ion to give manganese sulphate. Similarly the sulfurous acid, a portion of which becomes oxidized by the dissolved oxygen in the water dissolves the ferric hydroxide to form soluble ferric sulphate. Moreover, the

' acid condition of the water kills the iron bacteria and this aids in th removal of the accretions formed by them. It will be noted that while free 3:804, a strong acid, is formed, its formation is gradual by the action of the dissolved oxygen and thus is not formed in greater quantities than can be absorbed by the iron and other compounds. The manganese compounds heretofore have been the most difficult to remove since they are not attacked by the action of dilute acids or alkalisin the form in which they occur but must first undergo reduction.

My improved method is also eflective in breaking up rather large accretions known as mud balls which are apt to form in sand filters used in water purification after several months of service. In these secretions, the sand particleswhich also include some 0! the precipitate or fioc filtered out of the water, are bound together by the insoluble manganese, iron and lime compounds etc. These mud balls by reason of their high gravity work below the sand level of the filter and alter a heavy draw on the filter, release their entrained fioc thereby causing the filtered water to be turbid. The action of the sulfurous acid effectively breaks up these accretions and allows the fioc to be washed out.

While my invention is of particular usefulness in cleaning sand filters, it is also useful in removing insoluble deposits or similar nature occuring in various parts or water distributing systems.

Furthermore, while I have described a specific manner of applying the sulphur dioxide, I do not wish to be limited to this as many other modes of application will occur to those skilled in the art.

I claim:

1. The method of removing deposits containing hydrated manganese oxide in water treating and distributing systems which consists in treating said deposits with a dilute aqueous solution of S02.

2. The method of cleaning sand filters used in water purification which consists in treating same with an aqueous solution of 80:.

3. The method of cleaning sand filters used in water purification which consists in back flowin thereinto a dilute solution 01' SO: and removing the solution after the action thereof is complete.

4. The method of treating sand filters and the like which consists in establishing a water level intermediate of the height of the filters, adding to the water therein, then adding water by back flowing same to bring the water level to at least the level of the sand and then after the action 0! the SO: solution is complete, removing the solution.

JULIAN G. PATRICK. 

